1. Field of the Invention
The present invention relates to an apparatus for assembling a vehicle body, in which at least left and right side panels and a floor panel, out of all constituting members of the vehicle body, are combined by welding to thereby assemble the vehicle body.
2. Description of Related Art
As this kind of apparatus for assembling a vehicle body, there has hitherto been known the following one in Japanese Published Examined Patent Application No. 53073/1988. Namely, the apparatus comprises: a setting cart which is movable back and forth between a setting station and a vehicle body assembly station; and a jig which is mounted, in an inward-looking posture as seen laterally (i.e., from left or right), on a supporting base which is disposed on each of left and right outside portions of the vehicle body assembly station. The setting cart is provided with: floor panel supporting members for positioning and supporting a floor panel of the vehicle body; side sill receiving members for receiving left and right side sill portions which are defined as combined portions between the floor panel and the left and right side panels of the vehicle body; and side panel forcing members for forcing both the side panels from a lateral outside toward the floor panel. The floor panel and both the side panels are set in position onto the setting cart in the setting station and are transported to the vehicle body assembly station. In the vehicle body assembly station, each of the side panels on the setting bogy are received in a state of being combined to the floor panel by means of the jigs. In this state, each of the side panels is combined by welding to the floor panel to thereby assemble the vehicle body. In this apparatus, a plurality of welding guns are mounted on the jig, and the side panels are combined by welding to the floor panel by means of these welding guns.
The jig is specialized (or specially prepared) for each kind of the vehicle. If the welding guns are mounted on the jig as in the above-described conventional apparatus, the jig becomes higher in cost. If this kind of expensive jig must be prepared for each kind of the vehicle, the equipment cost becomes large.
In this case, the following arrangement is considered. Namely, on each lateral (left and right) side portions of the vehicle body assembly station, a plurality of welding robots are provided at a level below each of the jigs. Each of the side panels is thus combined by welding to the floor panel by means of these welding robots. In this arrangement, it is not necessary to mount the welding guns on the jig and, therefore, the equipment cost can be kept low.
However, if the welding robots are disposed in a manner as described above, during the welding work by the welding robots, the side sill receiving members and the side panel forcing members which are provided on the setting cart interfere with the welding robots. Therefore, the setting cart cannot be returned to the setting position. It follows that, after the side panels and the floor panel are received by the jig, the setting cart must be returned to the setting position first and, thereafter, the welding work by the welding robots must be started. The time required to return the setting cart to the setting position thus becomes a loss time, with the result that the cycle time becomes longer.
In view of the above points, the present invention has an object of providing an apparatus for assembling a vehicle body in which the welding work by welding robots can be started without waiting for the returning of the setting cart back to the setting station, whereby the cycle time can be shortened.
In order to attain the above and other objects, the present invention is an apparatus for assembling a vehicle body comprising: a setting cart movable back and forth between a setting station and a vehicle body assembly station; a jig mounted on a supporting base in a posture to look laterally inward, the supporting base being disposed on each laterally outside portion of the vehicle body assembly station; the setting cart having: floor panel supporting members for positioning and supporting a floor panel of the vehicle body; side sill receiving members for receiving side sill portions which are defined as combined portions between the floor panel and left and right side panels; and side panel forcing members for forcing each of the side panels from a lateral outside toward the floor panel; wherein the floor panel and both the side panels are set onto the setting cart in the setting station and are transported to the vehicle body assembly station, wherein each of the side panels is received in the vehicle body assembly station in a state of being combined with the floor panel by each of the jigs and wherein, in this state, each of the side panels is combined by welding to the floor panel to thereby assemble the vehicle body; a plurality of welding robots for combining by welding each of the side panels to the floor panel, the welding robots being disposed on each of the lateral sides of the vehicle body assembly station at a level below each of said jigs; wherein the side sill receiving members and the side panel forcing members are disposed on the setting cart so as to be retractable into shunted positions free from interference with the welding robots in welding operation.
According to the present invention, even if the welding work on the side panels and the floor panel by the welding robots is started immediately after the side panels on the setting cart are received by the jig in a state of being combined with the floor panel, the setting jig can be returned to the setting station without interference with the welding robots, if the side sill receiving members and the side panel forcing members are retracted into the shunted (or withdrawn) positions. In this manner, the welding work by the welding robots can be started without waiting for the returning of the setting cart back to the setting station. As a result, the cycle time can be shortened and the productivity can be improved.
Preferably, the apparatus further comprises a longitudinally elongated stationary frame positioned at a level below each of the jigs and the welding robots are mounted on the stationary frames so as to be longitudinally movable. Then, each of the robots can be made smaller in size and the welding of a plurality of longitudinal points can be done by each of the welding robots. Here, in the conventional apparatus for assembling a vehicle body, that supporting base for the jig which is disposed on each of the lateral sides of the vehicle body assembly station is formed into a longitudinally elongated rectangle in which the longitudinal length of an upper portion for mounting thereon the jig and the longitudinal length of a lower portion thereof are made equal to each other. If this kind of supporting base is used, all of the welding robots to be mounted on the stationary frame will lie behind the supporting base as seen from a lateral outside. Maintenance work such as electrode tip dressing of the welding guns to be mounted on the welding robots is performed by a worker who must enter into a space between the stationary frame and the supporting base. However, since this space is considerably small, the workability is poor, the load on the worker becomes heavy, and the work takes much time. This is a problem in improving the productivity. As a solution, the apparatus preferably comprises a supporting base formed into a T-configuration in which a longitudinal length of a lower portion thereof is smaller than a longitudinal length of an upper portion thereof for mounting thereon the jig, such that an open space which extends to the stationary frame is secured in a front and a rear at a lower portion of the supporting base. According to this arrangement, by gathering the welding robots on the stationary frame in those front portion and the rear portion of the stationary frame which face the open space in the lower front portion and the lower rear portion of the supporting base, the maintenance work of all the welding robots can be performed in the open spaces with a good workability. In this manner, the load on the worker in the maintenance work can be reduced and the working time can be shortened, resulting in the improvement in the productivity.
Further, in the above-described conventional apparatus for assembling the vehicle body, a drop lifter type of side panel setting device and a crane type of roof panel setting device are disposed in the setting station. After setting the floor panel on the setting cart, the side panels and the roof panel are set in position onto the setting cart by means of these setting devices. This conventional apparatus, however, has the following disadvantages. Namely, the side panel setting device and the roof panel setting device become large in size and scale. As a result, the space efficiency becomes poor and the freedom in the movement of the setting devices becomes smaller. Therefore, the position of feeding the side panels and the roof panel into the setting devices is limited and, consequently, the freedom of design in the distribution of the side panels and the roof panel is limited.
In this case, if the following arrangement is employed, the space efficiency is improved and the freedom of design in the distribution of the side panels and the roof panel increases. Namely, a setting robot made up of an articulated type of robot for the side panels is disposed on each lateral outside of the setting station, and a setting robot made up of an articulated type of robot for the roof panel is disposed on one lateral outside of the setting station in close proximity to the setting robot for the side panels. The side panels and the roof panel are thus set onto the setting cart by these setting robots.
Depending on the kind of the vehicle, there is sometimes employed the following way. Namely, that rear cross member such as a rear tray, rear roof rail, or the like which is laterally disposed in the rear portion of the vehicle body is not pre-assembled to the roof panel and the floor panel, but is set onto the setting cart as an independent member in the same manner as the side panels and the roof panel. In such a case, it is considered to provide a setting robot which is used exclusively for the rear cross member. This arrangement, however, becomes expensive. As a solution, preferably, the apparatus further comprises: a first setting robot made up of an articulated type of robot disposed on each of the lateral sides of the setting station to thereby set in position each of the side panels onto the setting cart by the first setting robot; a second setting robot made up of an articulated type of robot disposed on an outside of one of the lateral sides at a rear end of the vehicle body in the setting station; a roof panel holding device mounted on an operating end of the second setting robot; a rear cross member holding device mounted on a backside of the roof panel holding device at that end of the roof panel holding device which lies near a front end of the roof panel such that a lower surface of the rear cross member looks forward of the roof panel; wherein the rear cross member is set in that erected posture of the roof panel holding device in which the rear cross member holding device looks downward and wherein the roof panel is set in a horizontal posture of said roof panel holding device. According to this arrangement, when the roof holding device is made into the above-described erected posture by the operation of the second setting robot, the roof panel to be held by the roof panel holding device is erected in a position offset behind the rear of the vehicle body as compared with the rear cross member to be held by the rear cross member holding device. In this manner, the rear cross member can be set in a predetermined setting position in the rear of the vehicle body without interference of the roof panel with the side panels to be set by the first setting robot onto the setting cart. Then, while changing the posture of the roof panel holding device to a horizontal posture, the roof panel holding device is moved to an upper position between the left and right side panels. The roof panel is then set to a position between the upper edges of both the side panels. In this manner, the setting work of the rear cross member and the roof panel can be efficiently made in a continuous manner by means of the second setting robot. As compared with an arrangement in which separate setting robots are provided for the roof panel and for the cross member, respectively, the present apparatus can reduce the equipment cost.
The above-described jig is prepared for an exclusive use for each kind of the vehicle. Therefore, the jig must be exchanged or replaced whenever the kind of the vehicle is changed. As a jig exchanging device, there has hitherto been disclosed the following in Japanese Published Examined Patent Application No. 19756/1990. Namely, an apparatus frame which has a lifting space for vertically moving therein a jig is vertically provided in close proximity to one of front and rear positions in which a supporting base is disposed. Inside the lifting space, there is disposed a receiving base which receives the jig in an upward-looking posture, the receiving base being disposed in two vertical (upper and lower) stages by being supported by a lifting base which moves vertically inside the apparatus frame. When the supporting base is rotated into a phase in which the jig looks upward, the jig is exchangeable between the supporting base and the receiving base which is on the same exchanging level as the supporting base. According to this arrangement, the used jig which is mounted on the supporting base is changed into the upward-looking posture and, then, the used jig is transferred to either the upper or lower receiving base which is in the exchange position. Thereafter, the other of the receiving bases is moved to the exchange position. That jig for the next kind of the vehicle which is mounted in advance on this receiving base is transferred to the supporting base, whereby the jig exchanging can be performed. In this arrangement, however, in exchanging the jig, the jig must be made into the upward-looking posture by the rotation of the supporting base. It follows that the supporting base must be made rotatable, resulting in a higher cost. Therefore, in order to enable the jig to be quickly exchangeable while the jig is in an inward-looking posture, it is preferable to make the following arrangement. Namely, the apparatus further comprises: a supporting frame provided on the supporting base such that the jig is movable back and forth in an inward-looking posture; a jig replacing device disposed adjacent to one of the longitudinal sides of the supporting base, the jig replacing device having a rotary member which is rotatable about a longitudinal axis; a plurality of stock frames disposed in a periphery of the rotary member, the stock frames each supporting the jig so as to be movable back and forth, wherein, by the rotation of the rotary member, an arbitrary one of the stock frames is selected to be in an exchanging position which longitudinally aligns with the supporting frame, wherein the jig is replaceable in the inward-looking posture between the supporting frame and the stock frame selected in the replacing position. According to this arrangement, when the jig is exchanged or replaced, the empty stock frame is selected in the exchanging position by rotating the rotary member. The used jig is transferred from the supporting frame provided on the supporting base into this stock frame. Thereafter, the stock frame supporting the jig for the next kind of the vehicle is selected into the exchanging position. From this stock frame the jig for the next kind of the vehicle is transferred into the supporting frame. Since the jig can be transferred in the inward-looking posture between the supporting frame and the stock frame in the exchanging position, the supporting base need not be arranged to be rotatable only for the purpose of exchanging the jig, thereby preventing the equipment cost from increasing.
In addition, if the apparatus further comprises: a no pair of longitudinally elongated upper and lower guide rails fixed to a backside of the jig, the guide rails lying vertically opposite to each other when the jig is in the inward-looking posture; and upper and lower guide members provided on each of the supporting frames and the stock frames such that the upper and lower guide rails of the jig are engaged in a manner movable back and forth, the jig can be stably moved back and forth while the jig is in the inward-looking posture. Further, even if the posture of the rotary member is changed by the rotation of the rotary member, the jig can be prevented from dropping out of the stock frame. In this case, if the apparatus further comprises a releasing mechanism provided on each of the stock frames for releasing each of the guide members off from each of the guide rails by narrowing a distance between the upper and lower guide members, the engagement between the guide rails and the guide member can be released and another jig can be placed, instead, on each of the stock frames. It is thus possible to exchange many kinds of jigs without limit to the number of stock frames.